The research has three aspects: (1) Further understanding of the mechanism of transposition, and in particular the role played by host recombination - independent recombination in the process, and the mechanism underlying transposition-induced inversions of the host DNA. The system used will involve several transposons determining ampicillin resistance mainly Tn3 and Tn2660, a variety of plasmid replicons, and a series of transposition-defective mutants, and will focus on transposition from one site in a plasmid molecule to produce a duplication at another site (intramolecular transposition). Methods used will be largely genetical, supplemented by restriction-enzyme analysis and electron microscopy heteroduplexing. (2) Genetic and molecular analysis of the control of transcription of plasmid-borne Beta-lactamase using a series of ampicillin hyper-resistance mutants, some of which are known to have enhanced transcription of the gene. Methods used will be genetical, together with use of restriction-enzyme analysis, RNA polymerase binding and protection studies, DNA/RNA hybridization and DNA sequencing. (3) Analysis of microcin plasmids to determine if some microcins are carreid on transposons, and to examine interrelationships between a number of plasmids determining different microcins, studies by DNA/DNA hybridization, restriction-enzyme analysis and electron-microscopy heteroduplexing.